In space applications, it is necessary to be able to orientate certain elements, such as an antenna, a mast or a piece of equipment for example, of a satellite or of a space vehicle, in a predetermined direction in order, for example, to aim them towards an external target such as a planet, a receiver or an emitter, to keep them pointed towards a point on the surface of the earth, or alternatively to scan a particular region on the surface of the earth or of some celestial body. These positionings have often to be corrected in order to compensate for inevitable drift in the ability to maintain this direction and these numerous corrections mean that these space appendages and their supporting devices have to go through a high number of micro-rotation cycles. This phase is known as the fine pointing phase.
Given that placing a satellite into orbit is an irreversible operation, it is necessary, when designing the spacecraft, to ensure that these supporting devices will have a very long life, measured in terms of number of cycles, so as to guarantee their ability to withstand all these repeated stresses. For example, the life may exceed 300 000 cycles. Other requirements of the supporting devices include good mechanical integrity notably with regard to the external forces and bending moments applied to the supported shaft, good transverse rigidity, high-precision play-free guidance, significant amplitude of rotation for the flexible elements, typically of the order of 5 to 10° in both directions, positive and negative, and a low and constant resistive torque.
It is known practice to produce a support device for a rotary shaft using a pivot that has crossed flexible webs, notably a pivot of the kind known by the name of “Bendix freeflex pivot”. This type of pivot is not a through-pivot. It is therefore necessary to mount the supported shaft at one end only, in the manner of a cantilever, and this places significant stress on the webs of the pivot and transmits significant stress to the support structure, even in two-pivot setups. This type of pivot therefore offers limited mechanical integrity and transverse rigidity and does not satisfactorily meet all the requirements involved in creating a fine-pointing device.
It is also known practice to support a shaft using a device comprising two pivots consisting of ball bearings. A device such as this is subject to significant wear when subjected to reciprocating or oscillatory movements and therefore has a limited life. It too is unable satisfactorily to meet all the requirements involved in creating a fine-pointing device intended for space applications.
Patent application FR 2 703 415 describes a device for supporting a rotary shaft comprising a web-type through-pivot suited to the creation of a fine-pointing device, notably for space applications, although the angular capacity of the pivot is limited to small angles of rotation and becomes unsuitable as soon as the angular corrections required become greater.
It is an object of the invention to solve these problems and to propose a flexible-elements through-pivot with good mechanical integrity and ability to withstand the external forces and bending moments, good transverse rigidity, that allows high-precision play-free guidance, presents a low resistive torque, has a life able to withstand a great many rotational oscillations, at least in excess of 300 000, and that has an angular capability that is at least twice that of the pivot described in patent application FR 2 703 415.